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This article in SSSAJ

  1. Vol. 34 No. 2, p. 345-347
    Received: Feb 10, 1969
    Accepted: Oct 10, 1969

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Weight Loss on Ignition and K Fixation in Clays1

  1. C. E. Davis,
  2. N. Ahmad and
  3. Robert L. Jones2



A significant correlation (r2 = 0.65***) was obtained for K-fixation and loss on ignition in a number of soil clays of contrasting mineralogy and reference clay minerals when samples treated with K were heated hydrothermally (moisture saturated environment) and by dry heat from 100C to 380C. LOI (loss on ignition) values decreased with increase in temperature from 100C to 380C. At 100C, lower LOI values were obtained by hydrothermal treatment compared to dry heat but this was reversed at 200C. At 380C hydrothermal treatment resulted in lower LOI than dry heat for a high montmorillonite soil low in free Fe2O3, but there was little difference in the treatments for a montmorillonite soil high in free Fe2O3 and for soils rich in kaolinite. Loss on ignition was not markedly affected by the treatments for an illitic soil.

For high montmorillonite soils greater K fixation resulted from dry heat treatment at 100C but at higher temperatures, hydrothermal treatment was more effective. At higher temperatures, the dominantly kaolinite clays fixed more K in response to dry heat. Hydrothermal treatment (380C) was only heat treatment that promoted fixation in an illitic soil.

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